Peptide epitopes derived from non-mutated differentiation proteins that are widely expressed by cells of the melanocyte lineage and naturally presented by class I major histocompatibility complex molecules provide targets for vaccination-induced, cytotoxic T lymphocyte (CTL)-based immunotherapy of malignant melanoma. One of the key enzymes involved in pigmentation is the tyrosinase (Tyr) molecule that is expressed not only by malignant melanomas and normal melanocytes, but also by a broad range of human tissues as well. Available data for anti-self human Tyr (hTyr)-based clinical vaccination trials however shows that limited responses were observed in melanoma patients probably due Tyr-specific self-tolerance on the T cell repertoire limited the frequency and avidity of Tyr- reactive CTL. Since T cell receptor (TCR) transgenic mice have contributed to many aspects in understanding T cell ontogeny and selection of the peripheral repertoire, we propose to develop a TCR transgenic mice using a tyrosinase TCR that was previously isolated from a MHC class I- restricted CD4+ T cell isolated from the tumor infiltrating lymphocytes (TILs) of a HLA-A2+ patient with metastatic melanoma. This particular TCR (referred as TIL1383i) has been well characterized and is a co-receptor independent high affinity TCR. The avidity of TIL 1383i for peptide pulsed targets is 10-100-fold lower than most melanoma-reactive CD8+ T cell clones. In our first submission we hypothesized that owing to its origin and high affinity, this TIL1383i TCR may get selected again on a CD4 cell. Indeed we were able to successfully generate the TIL1383i TCR transgenic and our hypothesis proved to be partially correct when we got TIL1383i TCR expression on both CD4 and CD8 T cells. Surprisingly however the T cells passed thymic selection in mice with C57BL/6J background. Now we propose to carry out comprehensive analysis of this new transgenic mouse in context of tumor immunotherapy with the following aims: 1). To characterize antigen recognition and the functional avidity of CD4+ and CD8+ T cells from TIL1383i TCR mice. 2). To determine if CD4+ and CD8+ T cells in TIL1383i TCR mice can control the growth of B16/A2/Kb tumors. We believe that the T cells obtained from the proposed TCR transgenic mice would closely mimic the human T cells and thus the results obtained from the proposed study would help improve us in designing future immunotherapy trials using this unique TCR. PUBLIC HEALTH RELEVANCE: The goal of this project is to develop and characterize a transgenic mice bearing high affinity T cell receptor (TCR) reactive to tumor associated epitope tyrosinase. The high affinity TCR that was used to develop this TCR transgenic mice was isolated from a unique class-I restricted CD4 cell expanded from tumor infiltrating lymphocytes (TILs) of an HLA-A2+ patient with metastatic melanoma (thus referred as TIL1383i TCR). The unusual origin of the TCR and the unique founder obtained on C57BL/6J mice exhibiting TIL1383i TCR expression on both CD4 and CD8 T cell subsets makes this proposal unique since we now propose to understand the role of TCR affinity in tumor response by altering the signal strength of the TIL1383i TCR. This objective will be accomplished by breeding our TIL1383i/Tg mice with commercially available HLA-A2 and HLA-A/H2-Db mice. Successful completion of this proposal would provide us information about the feasibility of using this TIL1383i TCR in T cell adoptive immunotherapy protocols.